The prior art is replete with coin control systems which have been developed to determine whether proper coinage has been inserted to operate coin operated devices, and to detect the use of coins of improper size, weight, magnetic character, and other criteria. Such coin control mechanisms have become increasingly more complex as the art has developed. It has, therefore, been the object of this invention to provide a simple and accurate mechanism which will detect the use of oversize coins, undersized coins, and magnetic coins, and wherein the system has no moving parts but can be adjusted to accommodate coins of different sizes, and which can prevent retraction of the inserted coinage after the controlled device has been set in operation.